Recently, stereo camera apparatuses for measuring a distance to a subject by using a plurality of cameras mounted on a vehicle such as an automobile are known.
For detection of a three-dimensional object and measurement of a distance by using the stereo cameras, a method to acquire parallax at positions in an image is known. That is, the stereo camera sets two captured images as two standard images and vertically and horizontally subdivides the standard images into regions. The stereo camera evaluates the regions of the standard images sequentially, e.g., one pixel at a time, in a baseline direction in the standard images. The baseline direction corresponds to a direction connecting optical centers of two cameras of the stereo camera.